The Photochemistry of Organic Solids

Abstract During the years that he was at the Weizmann Institute of Science the late G. M. J. Schmidt initiated and developed a very vital research program on the relationship between the structures of organic crystals and the reactions which occur in these crystals. As the program developed the “solid‐state group” became larger and more diversified—X‐ray crystallographers, organic chemists, spectroscopists, and even theoreticans had their contributions to make. Professor Schmidt died in 1971. As one of the members of this group, I here present a review of recent developments in parts of the field of interest to me. Of the reactions of organic crystals which have been studied thus far a large number are induced by light and other radiation. This is because radiation, unlike most chemical reactants, can readily penetrate the surface of the crystal, and thus reach the sites one wishes to activate. It is my aim in this article to point out some of the principles operative in the photochemistry of organic crystals. I shall choose examples to illustrate these principles and will not attempt to cover all the various types of reaction and systems which have been studied. It is appropriate at this stage to pay tribute to the memory of another great scientist who recently passed away— Theodorr Föster. Many of the ideas which I develop here are extensions of Professor Förster's earlier work, as are so many of the recent developments in photochemistry.